The reason why yesterday's auction failure was so alarming was that it came amid a very public spat between the government and the Bank of England over whether Britain could afford a big spending splurge in the budget. Even without new spending pledges, the government has to raise at least £150bn through such auctions over the next year. In this context it cannot afford to give the impression that investors are not fully behind it – even occasionally.

Yesterday it struggled to raise the full £1.75bn it asked for. Today it managed to get more support for an auction to raise £1.1bn. It will have to repeat this performance week after week just to meet the current spending pledges – let alone make new promises of stimulus in the budget.

The likelihood is that the vast majority of these auctions will pass without notice, but there are two other reasons why the varying reaction of investors to these auctions is interesting. Yesterday's failed auction was for very long-term loans which are not covered by the Bank of England's quantitative easing program. This means that investors did not have the reassurance that the Bank would buy the debt back off them if the price falls too low. (quantitative easing, remember, involves buying government debt using newly created money to try to keep prices high and the cost of borrowing low)

In contrast, today's successful-auction was for index-linked loans, which are protected against future inflation risk. Given that one of the big fears about quantitative easing is that it will stoke up future inflation, what investors seem to be saying is that they will lend the government money but only if it promises to protect them if it all goes wrong: yet another financial guarantee we may struggle to keep.